Load bagging apparatus

ABSTRACT

A semi-automatic apparatus for facilitating the application of an inverted plastic film bag to a rectangular stack of articles, the stack presenting irregular side faces. An open rectangular frame is mounted for vertical movement between approximate floor level and above-the-stack level. A bag loaded on the frame at floor level is carried upwardly with the frame, aligned vertically with the stack, and then pulled downwardly over the stack, as the frame descends, by means of a series of four jawtype gripper units which are floatingly mounted at the corners of the frame and maintain the rim of the bag in an open condition. During descent of the frame a series of cams ride against the sides of the stack, compound their motion, and transmit it to the gripper units in such a manner that a clearance is at all times maintained between the open rim of the bag and the sides of the stack.

United States Patent [4 1 July 11, 1972 Lems 154] LOAD BAGGING APPARATUS [72] Inventor: Peter Lens, Wilmette, 111.

[73] Assignee: Slgnode Corporation, Chicago, Ill.

[22] Filed: March 8, 1971 2| Appl. No.: 121,706

[52 US. Cl. ..53/l87, 53/392 [51] lntCl. ..B65b43l28 [58] Field otSearell ..53/l87, 384. 256, 390, 392, 53/386, 243

[56] References Cited UNfl'ED STATES PATENTS 2,757,500 8/1956 Heinl et a1 ..53I392 X 3,308,601 3/1967 Masters ..53l256 3.47:,290 10/1969 Culpepper ....s3/392 x 3,568,402 3/1971 Lease et ....53/384 3,621,638 11/1971 Groclte ..53/386 Primary Examiner-Mn E. Condon Assistant Examiner-Horace M. Culver Aflomq-Blward R. Lowndee 1 1 ABSTRACT A semi-automatic apparatus for facilitating the application of an inverted plastic film bag to a rectangular stack of articles. the stack presenting in'egular side faces. An open rectangular frame is mounted for vertical movement between approximate floor level and above-the-stack level. A bag loaded on the frame at floor level is carried upwardly with the frame, aligned vertically with the stack, and then pulled downwardly over the stack. as the frame descends. by means of a series of four jawtype gripper units which are floatingly mounted at the corners ofthe frame and maintain the rim ol'the bag in an open condition. During descent of the frame a series of cams ride against the sides of the stack, compound their motion, and transmit it to the gripper units in such a manner that a clearance is at all times maintained between the open rim of the bag and the sides of the stack.

9Clalm8Dnwlnal-1aures *42 38114 34 lots X) PKTENTEDJuu 1 m2 SHEET 1 0F 2 INVENTOR. PETER LEMS LOAD BAGGING APPARATUS The improved bag-applying apparatus comprising the present invention has been designed for use primarily in connection with the application of a plastic heat-shrinkable film which is in the form of a commercially available bag to a generally rectangular stack of articles such as rectangular boxes, the stack presenting irregular side faces by reason of either differences in box dimensions or by irregular stacking of the articles. Tl-le invention is, however, not limited to such use and a bag-applying apparatus embodying the principles of the invention may, if desired, with or without modification as required, be employed in connection with the application of a bag-like covering to a wide variety of articles or stacks of articles, whether the same be rectangular or otherwise and regardless of whether the side faces of the load undergoing bagging are planar or irregular. irrespective of the nature of the articles undergoing bagging, or of the specific covering which is applied to the article the essential features of the invention are at all times preserved.

In the packaging of articles, it has been long the practice to cover the article with a film of heat-shrinkable material such as polyethylene or other plastic material and to thereafter subject the film-encased article to the action of heat so that, upon cooling of the film, it becomes firmly shrunk about the article. It has also been the practice to utilize a plastic film which is molecularly oriented in such a manner that shrinking of the film-covering takes place largely in a horizontal direction. Toward this end, plastic films which are folded into openended bag form, and molecularly oriented to give the desired horizontal and vertical shrinkage factors when shrunk upon an article, are commercially available, one such bag or film being shown and described in a copending application of Norbert J. Melsek, Ser. No. 88,6]3, filed Dec. 12, 1970 and entitled Palletized Load." The present invention relates to an apparatus by means of which a plastic film bag of this character may be conveniently applied to an article or load by a single operator and with a minimum of manual bag handling operatrons.

In the application of a bag of the character outlined above to a given load such as a tall rectangular stack of boxes or similar articles, the basic bag-manipulations which are required consist of supporting the stack on a suitable pallet, opening the rim of the bag to rectangular outline and holding it open so that it may be telescoped over the stack, aligning the open rim of the bag vertically with the stack, and finally progressively pulling the rim of the bag downwardly in telescopic relation with respect to the stack until the stack is enclosed by the bag film on four sides and over its top, with the film extending below the level of the pallet platform. In this condition the stack and pallet are conducted to the heatshrinking operation.

In the manual performance of these functions, considerable difficulty is encountered arising from the fact that ordinarily, for proper heat-shrinking functions, a maximum of l-inch spacing must be maintained between the bag and each side of the load. If the articles are unevenly stacked or if the stack otherwise presents non-planar side surfaces the difficulty is compounded. The usual procedure for a tall stack is for two operators, standing on ladders, to hold the bag open and slide it downwardly over the stack. Such a procedure is a difficult one and requires that the operators move from corner to comer as they progressively cause the rim of the bag to move downwardly over any projections, ledges or other surface irregularities, it being understood of course that each time projection is encountered the rim of the bag must be pulled outwardly away from the stack while downward pulling force is applied. A considerable degree of skill must be exercised to avoid bag rupture, to say nothing of repeated ladder-shifting operations, ladder climbing and descent, etc.

To obviate these difficulties various bag-supporting jigs have been devised. These jigs are usually in the form of bagholding racks which suspend the folded bag high above the load and are capable of being lowered as the rim of the bag is manually pulled downwardly around the stack but the difficulties encountered due to limited bag size still remain prevalent.

The present invention is designed to overcome the abovenoted limitations that are attendant upon either the manual or the semi-automatic bagging of articles for heat-shrinking purposes and, toward this end, the invention contemplates the provision of a largely automatic apparatus by means of which many of the manual operations which formerly gave rise to the difficulties outlined above are obviated.

Briefly, in carrying out the invention, the palletized load or stack is brought to the bagging station alongside a vertical pedestal which supports a horizontally disposed rectangular bag-supporting frame. The frame is mounted on the pedestal for movement between a lowered floor-level position alongside the stack where it may conveniently be loaded by manually applying a bag thereto, and a raised position wherein it clears the top of the stack. Jaw type gripper units at the four corners of the frame releasably hold the bag in a generally flattened horizontal position with the rim of the bag being spread out to rectangular configuration conformable to the horizontal outline of the stack and with the flattened bag being appropriately draped loosely over the frame bars. The frame is then raised on the pedestal slightly above stack level and is then swung angularly and laterally over the stack to bring the rim into vertical register with the stack, after which the frame is lowered around the stack so that the gripper units simultaneously pull the rim of the bag downwardly over the stack, thus progressively applying the bag in telescopic fashion thereto. Stack-sensing means are provided whereby the motion of a series of cams which ride on the side surfaces of the stack, is compounded and transmitted to the gripper units so that the latter remains at all times out of contact with the corners of the stack whereby the rim of the bag likewise is caused to clear the sides of the stack during descent of the frame. At such time as the frame, and consequently the rim of the bag, reaches substantially floor level, the gripper unit jaws are released and the empty frame, now clear of the bag, is then raised upwardly above stack level, swung laterally to clear the stack, and finally lowered to its initial loading position preparatory to commencement of the next succeeding stackbagging operation.

The provision of a bag-applying apparatus such as has been outlined briefly above and possessing the stated advantages, constitutes the principal object of the present invention. Other objects and advantages of the invention, not at this time enumerated, will become readily apparent as the nature of the invention is better understood.

In the accompanying two sheets of drawings forming a part of this specification, one illustrative embodiment of the invention has been shown.

In these drawings:

FIG. 1 is a fragmentary divided perspective view, showing the improved bag-applying apparatus of the present invention in its bag-loading position with respect to a stack of goods undergoing packaging;

FIG. 2 is an enlarged fragmentary side perspective view showing one of a series of bag-spreading gripper units employed in connection with the invention, the unit being shown in its bag-gripping condition;

FIG. 3 is a side perspective view similar to FIG. 2, showing the gripper unit in its position of bag release;

FIG. 4 is a fragmentary perspective view of a stack-sensing assembly embodying one of the gripper units of FIGS. 2 and 3 and showing the same in the position which it assumes at the commencement of the actual stack-bagging operation as the bag is initially applied to the upper end of the stack;

FIG. 5 is a fragmentary perspective view, similar to FIG. 4, showing the stack-sensing assembly in a partially lowered position with respect to the stack and illustrating the manner in which the gripper unit is caused to follow the contour of the stack;

FIG. 6 is a perspectivew view similar to FIGS. 4 and 5, illustrating the stack-sensing assembly in its position of bag-release after the bag has been caused to substantially completely envelop the stack;

FIG. 7 is an enlarged fragmentary perspective view looking in the direction of the arrows associated with line 77 of FIG. 4 and showing the details of a stack-sensing cam follower which is associated with the stack sensing assembly, the cam being detached, in the interests of clarity, from the frame on which it is mounted; and

FIG. 8 is a side view of a plastic bag of the type employed for bagging purposes in connection with the invention and showing the same in a substantially flattened condition.

Referring now to the drawings in detail and in particular to FIG. I, the bag-applying apparatus 10 of the present invention is shown as being operatively positioned with respect to a stack S consisting of a number of tiers of rectangular box-like articles 12, the stack as a whole being generally of rectangular configuration. The apparatus 10, in the position in which it is shown in FIG. 1, is adapted to receive an open-ended bag B of a heat-shrinkable plastic material at approximately floor level and, thereafter, to conduct the bag upwardly and position it over the stack S with its open rim in vertical register with the stack, after which the bag is lowered and pulled over the stack in telescopic fashion, much in the manner of applying a stocking to a limb. Subsequently the bag-encased stack is transported to a heating oven and subjected to a heat-shrinking operation to shrink the bag tightly about the stack. The heat shrinking operation forms no part of the present invention and no illustration thereof is made herein, the novelty of the invention residing solely in the apparatus by means of which the bag is applied to the stack, the apparatus being semiautomatic in its operation and serving to obviate many of the problems of bag-application which are present when the bag is applied solely by manual means or by present day semiautomatic bag handling equipment.

For illustrative purposes herein, and in order to demonstrate the full capabilities of the apparatus I0, the stack S is shown as being of irregular outline, the articles 12 in certain tiers having a slight overhang with respect to the articles therebeneath or thereabove so that the vertical sides of the stack are not precisely planar. A stack of this nature obviously offers limitations with respect to the manual telescoping of a plastic bag thereover, it being the principal aim of the invention to obviate these difficulties in a manner that will become apparent presently.

Still referring to FIG. 1, the stack 12 is preferably positioned on a suitable pallet 14 in order that the lower rim region of the bag B, when the latter is fully received over the stack, will extend below the underneath side of the stack so that during the heat-shrinking operation this rim region will shrink inwardly and permanently retain the bag film in its shrunk condition on the stack. The bag B assumes the form of a commercially available item which is constructed from a suitable heatshrinkable material such as polyethylene or polyolefin which is extruded from a molten resin through an annular die, expanded by a "blow-up" operation, and then stretched in a machine direction by suitabie nip rolls while the material is still soft, thus imparting to the film a molecular orientation which is largely longitudinal but which possesses some trans verse molecular orientation. The film is slit along one edge as it emerges from the nip rolls, leaving the other edge folded. The folded material is continuously wound on a core with the predominant molecular direction still extending longitudinally. To attain the desired molecular orientation in the completed bag, the bag film is severed from the core on which it is wound and the severed sheet of film is folded along a medial fold line which extends parallel to the direction of extrusion so as to bring the side portions of the folded sheet together in face-to-face contact, after which the meeting longitudinal edges of the folded sheet are heat-sealed together, thus producing an open-ended pocket between the sides of the sheet produced by the folding thereof.

Roughly speaking, the heat shrink factor of the plastic material is a function of the molecular orientation so that when the bag B is subjected to the action of heat at a predetermined temperature and for a predetermined period of time, as

the bag emerges from the heating operation and cooling sets in, a very appreciable reduction in the diameter of the bag takes place while only a moderate reduction in the axial extent of the bag results. It is to be ditinctly understood that no claim is made herein to any novelty associated with the processing of the plastic film material to produce the bag B nor with the heat-shrinking operation to which the bag is subjected in order to shrink the same on the stack S. The illustration of the bag B which appears in FIG. 8 is made solely for the purpose of facilitating an understanding of how such a bag is loaded into the apparatus 10 and of how the bag is handled by the apparatus during its application to the stack. In this view, die bag B is shown in its free state and in partially opened condition, the bag being generally rectangular in outline and presenting two thicknesses of the film material. The side edges of the bag are in the form of longitudinal heat-sealed seams 20 and the bag bottom" is in the form of a fold 22. The mouth of the bag exists by reason of two linearly straight bag edges 24. the bag is opened up by pulling these edges 24 apart at the time the bag is loaded into the apparatus 10, the apparatus having clamping facilities for maintaining the bag in its thus opened condition with the rim thereof conforming generally to the rectangular outline of the upper flat side of the stack 5 so that the bag may thereafter be pulled downwardly over the stack in a stocking-applying manner as briefly mentioned above and as will be described in detail presently.

Briefly, the apparatus It] involves in its general organization a substantially rectangular bag-receiving and supporting frame assembly 30 having rounded corner regions 32 on which there are installed a series of four bag-gripping and stack-sensing assemblies 34, each assembly including a floatingly mounted gripper unit 36 which releasably grasps the rim region of the bag and, in combination with the three other similar gripper units, holds the bag rim in its generally rectangular open condition during actual bag application to the stack S. Each as sembly 34 also includes a pair of stack-sensing cams 38 by means of which irregularities in the adjacent side surfaces of the stack are sensed, the sensing action of these two cams being compounded and transmitted to the associated gripper unit as the frame 30 descends in telescopic relationship over the stack for bag-applying purposes.

The frame is capable of both vertical movement bodily with respect to a vertically disposed supporting pedestal 40, and horizontal swinging movement about the axis of the pedestal so that a bag B which is loaded on the frame 30 and held in its open condition as stated above may be raised with the frame above the level of the stack S as shown in dotted lines in FIG. I, and then swung laterally as shown in broken lines to cause the open bag to register vertically with the stack. Thereafter, upon lowering of the frame, the gripper units pull the four corners of the open rectangular rim of the bag downwardly, thus telescoping the bag over the stack. During such telescopic lowering of the bag, the cams 38 ride against the sides of the stack S and, as they are displaced either inwardly or outwardly relative to the stack, their motion is compounded and transmitted to the gripper units 36 which are maintained a small distance away from the vertical corner edges of the stack so that the bag rim will not encounter any projections which may exist or otherwise become frictionally caught or retarded in its descent. This stack-sensing mechanism constitutes one of the principal features of the present invention. At such time as the frame 30 reaches floor level with the bag fully applied to the stack, a gripper-releasing foot 42 associated with each gripper unit 36 engages the floor and releases the jaws of the gripper unit so that the bag is freed from die frame 10.

Considering the apparatus 10 in greater detail, and still referring to FIG. I, the bag-supporting frame 30 is comprised of sections of tube stock suitable welded together so as to provide a substantially rectangular frame opening which is bounded by an inner or proximate frame bar 44, an outer or distal frame bar 46 and a pair of frame side bars 48. The frame bars 48 extend beyond the proximate frame bar 44, the extensions 50 thereof defining generally vertical triangular loops which converge inwardly toward the supporting pedestal 40 and straddle a vertically disposed tubular guide rod 54 which extends upwardly alongside the pedestal 40. Both the rod 54 and pedestal 40 extend upwardly an appreciable distance to a level which is somewhat higher than the height of the tallest stack which is capable of being bagged by the apparatus. For reasons that will be made clear presently, the guide rod 54 is mounted on the pedestal by upper and lower pin and link connections 56 and 58 respectively which allow for limited arcuate swinging movement of the guide bar about the vertical axis of the pedestal.

The aforementioned triangular frame bar loops 50 straddle the guide bar 54 in close proximity thereto and the frame assembly 30 as a whole is tractionally slidable vertically on the guide bar by means of two sets of small traction rollers including an upper set 60 which travels on the inner side of the guide bar (i.e., the side adjacent to the pedestal 40) and a lower set 62 which travels on the outer side of the guide bar. A conventional fast pin 64 is selectively receivable in a series of vertically spaced holes 66 provided in the guide bar 54 and is engageable with the lower regions of the two loops 50 for determining the lowermost position of the frame assembly 30.

The frame assembly 30 is adapted to be manually raised and lowered on the guide bar 54 and, in order to counterbalance the weight thereof, a cable 68 is attached to a suspension bridle yoke 70 and the latter, in turn is secured to the upper region of the frame bar loops 50. The cable 68 is held close to the guide bar 54 by a pulley 72 and passes over a second pulley 74 adjacent the upper end of the tubular pedestal and then downwardly into the pedestal and has a counterweight 76 attached to the free end thereof. The counterweight substantially balances the weight of the frame assembly 30 so that little manual effort is required for lowering or raising the same.

It will be understood that the bag must be loaded in the frame assembly 30 in an open condition, which is to say that the lower rim of the bag must be spread open to approximately rectangular configuration so that when the frame assembly is raised and swung to a position of vertical register with the stack S and then lowered as previously described, the bag will progressively envelop the stack. Accordingly, means are provided at the four corners of the frame proper for releasably gripping the rim region of the bag and holding it in a substantially square open condition while the remainder of the bag is loosely draped across the frame and, specifically, caused to rest on the distal and proximate frame bars 46 and 44 respectively. Accordingly, in order to maintain the bag in its thus draped position, two slightly tensioned coil springs 78 have their opposite ends fastened to these bars and closely overlie the medial regions thereof so that by manually raising the springs, the upper corner regions 80 (see also FIG. 8) may be tucked beneath these springs with the remainder of the bag being suspended in catenary fashion across the frame opening.

In order to hold the bag in its thus draped open-rim condition over the frame opening, the aforementioned bag-gripping and stack-sensing assemblies 34 are provided. Each assembly is comprised of one of the gripper units 36 the details of which are best seen in FIGS. 2 and 3, together with two of the stacksensing cams 38. The four assemblies 34 are operatively supported at the four corners of the frame proper as clearly shown in FIG. I. Since the four assemblies 34 are identical in construction, a description of one of them will suffice for them all.

Each bag-gripping and stack-sensing assembly 34 involves in its general organization a gripper-supporting anglepiece 82 which, in FIGS. 4, 5 and 6, is shown as underlying the corner or juncture region between the frame bars 46 and 48, the anglepiece being of right angle construction and having its apex region suspended from the frame 30 by means of a short length of flexible cable 84. The outer end of each arm of the anglepiece is pivotally secured to the lower regions of the associated earns 38, the upper regions of such cams being pivotally supported on the frame bars in a manner and for a purpose that will be made clear presently. The anglepiece is thus loosely and pivotally suspended from the adjacent corner region of the frame proper for compound swinging movement both in the vertical planes of both frame bars 46 and 48, as well as laterally with respect to these planes due to the compounding of these swinging motions and the ability of the cams 38 to flex in a manner that likewise will be made clear subsequently.

Referring now to FIGS. 2 and 3, each gripper unit includes a gripper anvil which is welded as indicated at 92 to the corner region of the anglepiece 82 and which therefore may be regarded as being a fixed member. This fixed gripper anvil 90 is provided with a fixed gripper jaw 94 which is designed for cooperation with a movable gripper jaw 96 provided on a movable jaw member 98 in the form of an elongated arm which is pivoted by a pin 100 to the fixed anvil member 90.

The jaw member 98 is movable between the open position wherein it is shown in FIG. 3 and the closed position of the FIG. 2, it being understood, of course, that the two gripper jaws 94 and 96 are adapted to receive therebetween a limited portion of the open rim of the bag B as shown in FIGS. 1, 4 and S, and, in combination with the jaws associated with the three other gripper units 36, maintain the rim of the bag in its wide open rectangular condition preparatory to and during bag application to the stack S.

The movable jaw member 98 is generally of open cage-like construction as clearly shown in FIG. 1, the cage straddling the anvil member 90 and being provided with a transverse limit stop bar 102 designed for engagement with an edge of the anvil 90 to determine the fully open position of the gripper jaws 94 and 96. A pair of triangular plates 104 are welded to the underneath side of the movable jaw member 98 and a pair of tension springs 106 which extends between these plates and the gripper anvil 90 serves to establish an over-center position for the jaw member so that the spring will maintain the latter either in its open or its closed position with respect to the fixed jaw 94.

Still referring to FIGS. 2 and 3, the aforementioned gripperreleasing foot 42 is carried at the lower end of a release arm 108 which has its upper end pivoted by the pin 100 to the anvil 90. The release arrn 108 normally assumes the full-line position in which it is shown in FIGS. 2 and 3 wherein an edge portion thereof bears against a shoulder I10 on the gripper anvil but, at such time as the foot 42 comes into contact with the floor or other foundation surface on which the apparatus 10 is mounted, during lowering of the frame assembly 30, the foot 42 and its associated arm 108 are shifted to the dotted line position of FIG. 3 so that a second transverse bar 112 carried by the arm engages the adjacent edges of the two triangular plates and thus shifts the jaw arm 98 to its position of jaw separation with respect to the anvil 90, the springs 106 serving to maintain the jaw arrn so positioned until it is manipulated during a succeeding stack-bagging operation.

The details of the various stack-sensing earns 38 are best illustrated in FIGS. 4 to 7 inclusive, particularly this latter view. Each cam is in the form of a length of flat sheet metal stock having reverse bends at its opposite ends and establishing an upper reentrant loop "3 and a lower reentrant lobe-forming loop 114. The upper loop I 13 encircles the adjacent frame bar 46 or 48, as the case may be and is pivoted thereto by a stud 116 (FIG. 7) which projects from an anchor block llfl secured by bolts 120 to the distal end region of the reentrant loop 112 and within the confines of the latter. A cotter pin I22 holds the pin against undue endwise shifting movement relative to the frame bar.

The lower portion of the cam 38 is pivotally connected to the adjacent end of the horizontal anglepiece 82 by a throughbolt 124 which passes through the distal end of the reentrant loop "4, a cotter pin 126 passing through the pin to complete the releasable connection.

From the above description it will be apparent that each of the four bag-gripping and stack sensing assemblies 34 is adapted during lowering of the frame assembly 30 over the stack 8 to operate in the vicinity of one of the vertical corners of the stack, the gripper unit 36 functioning to pull the adjacent comer region of the bag rim downwardly along such corner, while at the same time the two sensing cams ride against the adjacent opposed side of the stack so that their respective follower movements are compounded and transmitted to the anglepiece 82 and to the gripper anvil 90 which is fixedly secured thereto. The nature of this compound movement of the gripper anvil will be described in detail presently when the operation of the apparatus 10 as a whole is set forth, it being sufficient for the present to state that the gripper anvil, and consequently the bag-gripping jaws associated therewith is at all times maintained out of contact with the corner region of the stacks so that the corner region of the bag opening which is being pulled downwardly by the gripper unit will not encounter any interference by the stack.

OPERATION OF THE APPARATUS In the operation of the apparatus 10, the operator will select the appropriate hole 66 for placement of the fast pin 64 in the guide rod 54 to adjust the lower position of the frame 30 to his particular preference and then he will cause the frame to assume the position of FIG. I slightly above floor level and with the bag-gripper units 36 in their positions of release as shown in FIG. 3. At this time, the release feet 42 will be out of contact with the floor. With the frame in this position, bag-loading operations are commenced.

The bag B is loaded onto the frame by tucking the bag corners 80 between the springs 78 and the frame bars 44 and 46 while the four gripper units 36 are caused to engage the rim of the bag at quadrilateral regions therearound. This closing of the gripper jaws upon the rim of the bag may be accomplished by a single operator who will initially apply one gripper unit to the bag rim and then stretch one section of the bag rim in the direction of an adjacent gripper unit to make the second gripper application. The third and fourth applications are made in the same way. After the jaws 94 and 96 of all the gripper units have been closed upon the rim of the bag, the latter will assume approximately the draped condition of FIG. 1.

The actual jaw closing operations which are performed on the gripper units 36 are efi'ected by holding the bag rim with one hand and manipulating the movable jaw member 98 with the other hand to pull it past its dead center position so that the spring 106 will bias this member to its jaw-closing position. It is to be noted that with the bag thus draped across the frame, the various anglepieces 82 are pulled inwardly toward the center of the frame so that the cams 38 are maintained under flexion and their lower lobes ll4 are displaced inwardly. This flexion of the spring steel cams serves to hold the rim or the bag taut.

With the bag B thus loaded on the frame 30, the operator will then raise the frame manually be engaging any convenient portion thereof and applying a lifting force thereto. As the frame rises, the counterweight 76 descends within the tubular pedestal 40. After the frame 30 has been elevated above the level of the upper end of the stack S, it is swung bodily about the axis of the pedestal and is brought into vertical register with the stack. Small adjustments for discrepancies in stackto-pedestal distance may be made by causing the upper lower articulated pin-and-link connections 56 and 58 to adjust themselves for such discrepancies.

When proper stack and frame alignment has been effected, lowering of the frame about the stack is progressively resorted to as illustrated in FIGS. 4,5 and 6. Upon initial descent of the frame 30, the lower lobes 114 of the link-like spring steel stack-sensing cams 38 will engage the upper comer edges of the stack 8 and ride outwardly onto the adjacent side faces as shown in FIG. 4. At this time the aforementioned compounding of the motions of each pair of cams will take place and be transmitted to the anglepieces 82, thus causing them to move diagonally outwardly so as to maintain the jaws proper 96 and 94 out of contact with the stack.

It is to be noted at this point that the cams 38 are capable of outward flexing movement relative to the adjacent stack sides, as well as limited lateral swinging movement, outward motion of one cam resulting in a slight swinging movement of its counterpart cam and vice versa since the direction of flexion of the one cam is the same as the direction of pivotal swinging movement of the other cam. The two cams 34 will thus ride over the various overhanging ledges on the irregularly shaped stack as shown in FIG. 5 and, during the entire descent of the frame assembly 30 maintain the gripper unit slightly spaced from the comer region of the stack. As previously stated in the commercial bagging of stacked articles for heat-shrinking pur poses, it has been customary to utilize plastic bags which envelop the stack with a potential clearance on the order of only I inch between the sides of the bag and the sides of the stack. This small clearance constitutes the principal difficulty which is encountered in the manual application of a bag film to a stack. Because of the presence of the stack-sensing cams 38 which compound and transmit their motion to the gripper units 36, this difiiculty is obviated, because not only the corners of the bag opening, but the entire rim of the bag is at all times maintained clear of the stack and well within the elastic limit of the film material.

As the frame 30 approaches floor level, the gripper release feet 42 will move into contact with the floor surface, it being understood that at some time before lowering of the frame assembly has commenced the operator will have withdrawn the fast pin 64 from the hole 66 in which it has been installed. As soon as each foot 42 engages the floor, continued downward movement of the frame will cause the stop bar 112 to engage the adjacent edge of the triangular plates 104 as shown in the dotted line position of FIG. 3, thus shifting the movable jaw member or arm 98 over its dead center position and allowing the springs 106 to pull this jaw member to its fully open posinon.

It will be understood that during the entire descent of the frame 30 the rim of the bag B will have been pulled downwardly and, as a consequence, the four sides of the stack will have become enveloped by the bag which then conforms to the rectangular contour of the stack, while at the same time the upper region of the bag will have been drawn downwardly against the upper face of the stack.

With the rim of the bag thus released by the various gripper units 36, the flexion in the cams is released so that these cams move clear of the stack. The frame assembly may thus be raised without interference from the stack and then swung to its out-of-the-way position illustrated in dotted lines in FIG. I, and finally lowered to its full line position just above floor level preparatory to the next succeeding bagging operation. Prior to descent of the frame assembly, the operator will replace the fast pin 64 in the selected hole 66 to afford floor clearance for the gripper release feet 42 so that the movable jaw arms may be swung to their open positions.

It will be understood that successive stacks S which are to be bagged may be conducted to and from the bagging station BS on a suitable conveyor (not shown) which is operable under the control of the operator and which may lead directly to the heat-shrinking oven if desired.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit of the invention. Therefore, only insofar as the invention has particularly been pointed out in the accompanying claims is the same to be limited.

Having thus described the invention, what I claim and desire to secure by letters patent is:

1. In an apparatus for progressively pulling an open-ended plastic bag film downwardly over a fixedly supported load, in combination, a frame support positioned in the vicinity of the load, a bag-receiving frame presenting a central frame opening mounted on said support for vertical and horizontal movement from a loading position laterally alongside the load to a position wherein the frame opening is in vertical register with the load, and then downwardly in surrounding bag-pulling relationship with respect to the load, and releasable gripper means disposed at spaced regions around the frame opening and engageable with the rim of a bag which is loaded on the frame in the loading position thereof for maintaining said rim in an open condition during downward descent of the frame about the load.

2. The combination set forth in claim 1, wherein said releasable gripper means comprises a pair of cooperating gripper jaws movable relative to each other between closed bag-engaging and open bag-releasing positions, and means engageable with the load and effective during downward bagpulling descent of the frame for maintaining said jaws, and consequently the rim of the bag, out of contact with the load.

3. In an apparatus for progressively pulling an open-ended plastic film bag downwardly over a rectangular floor-supported load, in combination, a support adjacent the load, a horizontally disposed rectangular bag-receiving frame presenting a central frame opening and mounted on said support for both vertical and horizontal shifting movement whereby the frame is movable bodily from a loading position at floor level alongside the load vertically to an intermediate raised position above the uppermost level of the load, and then horizontally to a position wherein said frame opening is in vertical register with the load, and finally downwardly in surrounding bag-pulling relationship with respect to the load to substantially floor level, and releasable gripper means disposed at each corner of the frame opening and engageable with the rim of a bag which is loaded on the frame in the loading position thereof for maintaining said rim in an open rectangular condition during downward descent of the frame about the load.

4. The combination set forth in claim 3, wherein said frame projects radially outwardly from said support and has its inner end pivotally and slidably connected thereto for vertical sliding movement of the frame during travel of the latter from its loading position to its raised intermediate position, as well as during its downward movement, and for horizontal swinging movement about the axis of the support during travel of the frame from its raised intennediate position to its position of register with the load.

5. The combination set forth in claim 4, wherein said releasable gripper means at each corner of the frame comprises a pair of cooperating gripper jaws movable relative to each other between closed bag-engaging and open bag-releasing positions, and rneam engageable with the load and effective during downward bag-pulling descent of the frame for maintaining said jaws, and consequently the rim of the bag, out of contact with the load.

6. The combination set forth in claim 4, wherein said gripper means comprises a fixed jaw member floatingly suspended from said frame for universal swinging movement, and a cooperating movable jaw member pivoted thereto, said movable jaw member being movable relative to the fixed jaw member between closed bag-gripping position and an open bag-releasing position and cam means mounted on the fixed jaw member and slidably engageable with the load during downward movement of the frame for maintaining said fixed jaw member and consequently the adjacent portion of the bag rim which is held thereby, spaced from the load during such downward movement of the frame.

7. The combination set forth in claim members, one wherein said cam means comprises a pair of cam members, one of which is engageable with one vertical side of the load and the other of which is engageable with an adjacent side of the frame.

8. The combination set forth in claim 7, wherein each cam member is of link-like construction, has its upper end pivoted to the frame and its lower end effectively pivoted to the fixed jaw member and, in part, establishes the floating suspension of the latter from the frame. I I

9. The combination set forth in claim 8, wherein each cam is famed of spring material, the pivotal connection between its upper end and the frame allows for free lateral swinging movement thereof in a plane parallel to the general plane of the side of the load with which it is engageable, and for restrained swinging movement under flexion in a direction toward and away from the load. 

1. In an apparatus for progressively pulling an open-ended plastic bag film downwardly over a fixedly supported load, in combination, a frame support positioned in the vicinity of the load, a bag-receiving frame presenting a central frame opening mounted on said support for vertical and horizontal movement from a loading position laterally alongside the load to a position wherein the frame opening is in vertical register with the load, and then downwardly in surrounding bag-pulling relationship with respect to the load, and releasAble gripper means disposed at spaced regions around the frame opening and engageable with the rim of a bag which is loaded on the frame in the loading position thereof for maintaining said rim in an open condition during downward descent of the frame about the load.
 2. The combination set forth in claim 1, wherein said releasable gripper means comprises a pair of cooperating gripper jaws movable relative to each other between closed bag-engaging and open bag-releasing positions, and means engageable with the load and effective during downward bag-pulling descent of the frame for maintaining said jaws, and consequently the rim of the bag, out of contact with the load.
 3. In an apparatus for progressively pulling an open-ended plastic film bag downwardly over a rectangular floor-supported load, in combination, a support adjacent the load, a horizontally disposed rectangular bag-receiving frame presenting a central frame opening and mounted on said support for both vertical and horizontal shifting movement whereby the frame is movable bodily from a loading position at floor level alongside the load vertically to an intermediate raised position above the uppermost level of the load, and then horizontally to a position wherein said frame opening is in vertical register with the load, and finally downwardly in surrounding bag-pulling relationship with respect to the load to substantially floor level, and releasable gripper means disposed at each corner of the frame opening and engageable with the rim of a bag which is loaded on the frame in the loading position thereof for maintaining said rim in an open rectangular condition during downward descent of the frame about the load.
 4. The combination set forth in claim 3, wherein said frame projects radially outwardly from said support and has its inner end pivotally and slidably connected thereto for vertical sliding movement of the frame during travel of the latter from its loading position to its raised intermediate position, as well as during its downward movement, and for horizontal swinging movement about the axis of the support during travel of the frame from its raised intermediate position to its position of register with the load.
 5. The combination set forth in claim 4, wherein said releasable gripper means at each corner of the frame comprises a pair of cooperating gripper jaws movable relative to each other between closed bag-engaging and open bag-releasing positions, and means engageable with the load and effective during downward bag-pulling descent of the frame for maintaining said jaws, and consequently the rim of the bag, out of contact with the load.
 6. The combination set forth in claim 4, wherein said gripper means comprises a fixed jaw member floatingly suspended from said frame for universal swinging movement, and a cooperating movable jaw member pivoted thereto, said movable jaw member being movable relative to the fixed jaw member between closed bag-gripping position and an open bag-releasing position and cam means mounted on the fixed jaw member and slidably engageable with the load during downward movement of the frame for maintaining said fixed jaw member and consequently the adjacent portion of the bag rim which is held thereby, spaced from the load during such downward movement of the frame.
 7. The combination set forth in claim members, one wherein said cam means comprises a pair of cam members, one of which is engageable with one vertical side of the load and the other of which is engageable with an adjacent side of the frame.
 8. The combination set forth in claim 7, wherein each cam member is of link-like construction, has its upper end pivoted to the frame and its lower end effectively pivoted to the fixed jaw member and, in part, establishes the floating suspension of the latter from the frame.
 9. The combination set forth in claim 8, wherein each cam is formed of spring material, the pivotal connection between its upper end and the frame allows for free lateral swinging moveMent thereof in a plane parallel to the general plane of the side of the load with which it is engageable, and for restrained swinging movement under flexion in a direction toward and away from the load. 